What is the proper overload size for a 230 Volt, single phase, 3 HP motor rated at 14 Amps with a 40°C temperature rise?

To determine the proper overload size for a 230 Volt, single-phase, 3 HP motor rated at 14 Amps with a 40°C temperature rise, it's essential to understand how overload protection is calculated for motors. The overload size is commonly based on the motor's full-load current rating.

Generally, for a motor, the overload protection should be set at a value that adequately protects the motor from overheating while allowing for normal operational variances. In this case, the rated full-load current for the motor is given as 14 Amps.

When selecting the overload size, the National Electrical Code (NEC) typically recommends setting the overload at 125% of the full-load current for motors. This means you would calculate 125% of 14 Amps to find the correct overload setting.

Calculating that gives:

1. 125% of 14 Amps = 1.25 x 14 = 17.5 Amps.

Therefore, the overload size of 17.5 Amps allows for the necessary protection against overloads while accommodating the 40°C temperature rise of the motor. It ensures that the motor can handle brief surges in current without tripping unnecessarily while still providing adequate protection.

Understanding this calculation